Effect of external stress on ferroelectricity in epitaxial thin films
Effect of external stress on ferroelectricity in epitaxial thin films
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DOI：
10.1103/physrevb.66.214108
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发表时间：
2002-12
影响因子：
3.7
通讯作者：
A. Emelyanov;N. Pertsev;A. Kholkin
中科院分区：
文献类型：
--
作者：
A. Emelyanov;N. Pertsev;A. Kholkin
用非线性热力学理论描述了外加机械载荷对生长在不同立方衬底上的外延薄膜的铁电、介电和压电性能的影响。在薄膜上表面均匀加载的近似下，对单畴钙钛矿薄膜进行了计算。给出了外延薄膜的“失配应变-应力”和“应力-温度”相图。结果表明，加载会导致薄膜偏振态的剧烈变化。最引人注目的理论预测是应力诱导的铁电到顺电的相变，这种相变可能发生在室温下生长在“压缩”衬底上的薄膜中，这种衬底在外延系统中提供了很大的负失配应变。计算了单结晶膜的小信号介电常数和压电常数，发现在某些失配应变-温度条件下，薄膜对外应力非常敏感。因此，该理论预测，铁电薄膜的机械加载可以用来微调其物理性质。计算结果也可用于解释通过扫描力显微镜和铁电薄膜压痕获得的实验数据。
A nonlinear thermodynamic theory is used to describe the influence of an external mechanical loading on the ferroelectric, dielectric, and piezoelectric properties of epitaxial thin films grown on dissimilar cubic substrates. The calculations are performed for single-domain perovskite films in the approximation of a homogeneous loading of the film upper surface. The ``misfit strain-stress'' and ``stress-temperature'' phase diagrams are developed for epitaxial ${\mathrm{PbTiO}}_{3}$ and ${\mathrm{BaTiO}}_{3}$ films. It is shown that the loading may lead to drastic changes of the film polarization state. The most remarkable theoretical prediction is the stress-induced ferroelectric to paraelectric phase transition, which may take place at room temperature in films grown on ``compressive'' substrates that provide large negative misfit strains in the epitaxial system. The small-signal dielectric and piezoelectric constants of single-domain ${\mathrm{PbTiO}}_{3}$ and ${\mathrm{BaTiO}}_{3}$ films are also calculated and found to be very sensitive to the external stress under certain misfit strain-temperature conditions. The theory thus predicts that the mechanical loading of ferroelectric films can be employed for the fine tuning of their physical properties. The results of calculations may be also useful for the interpretation of experimental data obtained via scanning force microscopy and the indentation of ferroelectric films.